VSE: How can I cache 3d scenes for faster editing?
I just setup a simple scene in Blender 2.82.7 and addet it in a new scene to the VSE. After one playback Blender seems to automaticly cache Frames ant the playback is realtime. Blender Docks

Ther is an option to prefetch frames .. but this semse to be brocken as of right now (2.82.7) https://developer.blender.org/T70612

Nevertheless caching seems to work.

Create animation


Create new Scene.001 and add the Scene with animated cube to Sequencer.


Start Playback and wait for all frames to get rendered once. Blender will skip Frames trying to keep realtime playback up as best as possible, but eventualy all frames will be cached. (probably untill no more frames fit into RAM)


Otherwise the goto way to work in the VSE is to render out your animation scenes in image Sequences and compose them in the VSE afterwards to render your final encodet video file. This way you have them on disk no matter wat happens and can rerender frames you need to change.

For indepth information see Video Editing Workflow: Use a separate scene for VSE?
and 
Movie editing : VSE or compositor?